1. Field of the Invention
The invention provides a method and plant for cooling fluids in the liquid state, possibly also containing solid elements, by means of a cooling fluid consisting of a liquefied gas such as N2, CO2, Ar or a mixture thereof, the cooling fluid passing into the gaseous or vapour state following the heat transfer.
2. Related Art
As is widely known, to cool a liquid, apparatus or plants are usually used having surfaces of separation between the cooling fluid and the fluid to be cooled. However, this solution necessarily implies a low overall heat transfer coefficient and a mechanical action on the fluids due to the friction between these and the separation surfaces. This mechanical action limits the use of this type of apparatus if this phenomenon can degrade the organoleptic characteristics of the fluid to be cooled, such as in the case of pressed grape pulp.
A method for cooling fluids using liquefied gases is already known from a previous patent of the same applicant. That patent (IT1313938) describes a method for cooling a liquid in a controlled manner using liquefied gases as coolants, said liquid possibly also containing solid bodies. The method consists of feeding said liquid to be cooled into a containing member, also feeding into said member a suitable quantity of liquefied gas such that this latter comes into direct contact with said liquid, this contact leading to the transformation of the liquefied gas into a gaseous phase and to the cooling of the liquid, said gas or vapour and said cooled liquid then being extracted from the containing member.
In this prior patent a conduit is provided to transfer the cooled fluid and the gas or vapour, generated during heat transfer by the apparatus in which the heat transfer takes place, to the apparatus in which the two fluids are separated, this conduit being traversed by the fluids at high velocity so that both the cooled liquid, or two-phase solid-liquid mixture, and the cooling fluid in the gas or vapour state are transferred simultaneously.